Good luck getting Sheldon Cooper to solve this problem: At what point in this season of The Big Bang Theory did Sheldon turn into someone almost completely unrecognizable from the man he’s become over the last few years?

On tonight’s episode, Sheldon seemed to fall deeper into self-absorbed territory by becoming territorial over his fiancé’s work hours and work partner. It follows a pattern of unusual behavior this season that seems to have undone some of his profound personal growth over the latter half of the series. So what gives? Where’s the Sheldon who was vulnerable, supportive, and, yes, even romantic?

In “The Collaboration Contamination,” Sheldon and Raj confide in Bernadette that they can’t handle Amy and Howard working together. Raj is just lonely without his “work wife” Howard to keep him company—no point in dissecting that one—but Sheldon acts possessive over Amy, demanding to know why she’s working late after her first day with Howard. This was after he already dropped in on them at work to make sure everything was going alright. Then, in another scene, he complains that they’re working on a Saturday. “Is this how you envisioned your weekend?” he angrily asks Bernadette. Who is this guy?

It’s a question I’ve been thinking about since the season 11 premiere, when he got jealous that he wasn’t being peppered with questions about his success while meeting Amy’s work colleagues. Of that episode, I wrote: “Perhaps the only downside [of the episode] was Sheldon being a complete ass…when Amy was shown more attention by colleagues at a work dinner than him.”

Things didn’t get better in episode two, when Amy had to deal with Sheldon acting like a jealous child after she confided that she got special lab equipment at work. To make matters worse, we also found out Amy often keeps her success a secret from him so he doesn’t get upset. Much to my disappointment, I noted that Sheldon had turned into a mopey, outdated stereotype of a man who can’t handle a woman’s success.

PHOTO: Michael Yarish/Warner Bros.

Maybe that’s why I was beyond bored when episode three spent nearly 20 minutes having Sheldon drive himself mad trying to pick a perfect wedding date. I would have rather he spent that time in therapy trying to figure out why he’s become so frustratingly annoying this season. He briefly redeemed himself in episode four while assuring Howard he’d be a good father to his son, but it all seemed to unravel tonight. “This whole thing is maddening,” he vented to Bernadette about Amy’s work schedule. “I just wish I could make Howard feel as angry as I’m feeling.” What? He’s angry that his fiancé is working on a big laboratory project with their friend? Haven’t we moved past this old-fashioned trope of being jealous over working with a member of the opposite sex?

Later in the episode, when Leonard tells Sheldon that he needs to get over it (finally, someone with some common sense), Sheldon shuts him down and says, “It is a big deal! Howard is getting Amy used to laughing and listening to music! What if she expects that madness at home?” It’s all meant to be cute and funny, but I wasn’t laughing. Sheldon sounds like he wants to keep Amy trapped in the 1950s rather than embark on a lifetime of happiness. If I’m supposed to be excited that these two are heading toward a wedding, then here’s a news flash: I’m not.

Perhaps the reason I’m most annoyed with Sheldon’s arc this season is that the show has done such a stellar job in recent years of truly growing these characters. It’s no longer a series about four clueless male scientists who ogle the girl next door. The series has embraced real-life issues such as pre-and post-partum depression, gender stereotypes, marital issues, and mental health and done so with humor. To go back now seems like such a waste. And if anything is going to make Sheldon angry, that should be it.